1. Field of the Invention
The present invention relates to displaying apparatuses, and more particularly, to a displaying apparatus whose power supply is cut off in response to power supply to a computer main body being cut off.
2. Description of the Related Art
In general, personal computer systems are categorized into portable computers and desktop computers. The former comprises a system body integrally combined with a displaying apparatus, whereas the latter comprises a computer main body and a displaying apparatus, both of which are separate from each other.
The displaying apparatus of the desktop computers is connected to the computer main body by a connector, and processing picture signals are supplied to the displaying apparatus from a video card provided within the computer main body.
FIG. 4 shows a conventional displaying apparatus of a desktop computer having a liquid crystal display (LCD) monitor. The displaying apparatus comprises a D-sub connector 31 connected to a video card (not shown) of a computer main body (not shown), a video signal processing unit 33 which processes horizontal/vertical (H/V) synchronous signals and RGB signals supplied through the D-sub connector 31, an LCD panel 35 which displays picture signals processed in the video signal processing unit 33, a power circuit unit 43 which converts commercial alternating current (AC) power into driving powers (1.5V and 3.3V, etc.,) and supplies the driving powers to each of signal processing units (for example, the video signal processing unit 33 and the LCD panel 35), and a controlling unit 39 which controls the power circuit unit 43 to supply the driving powers to each of the signal processing units in response to a power switch 37 being selected to be power-on.
Here, the computer main body and the displaying apparatus of the desktop computer have their own power switches. Accordingly, the respective power switches of the computer main body and the displaying apparatus need to be turned on or off separately when the computer system is turned on or off, thereby making it inconvenient to use the desktop computer system.
To solve this problem, displaying apparatuses have recently employed a power controlling method in which power supplied to each driving circuit from a power circuit unit is interrupted where synchronous signals are not inputted through a D-sub connection port. However, voltages are continuously supplied to a sensing circuit which senses the synchronous signals even though a video card is not in operation because power supplied to the computer main body is cut off. Therefore, a maximum power saving effect is not realized.